It's a grub, the youngster of a beetle. Which particular one is difficult to say without a close look. Very large ones are common in compost. If that's where it's from, it won't damage living plants.

Ignore any comments which say you have Japanese beetles. They're not in CA ... yet.

its a grub of some sort ...

it eats roots.. usually of grass ..

until it turns into something like a jap. beetle.. then it devours the top of your plants ...

treat you lawn accordingly ...

the real key.. is how many you find per square foot ... a dozen or so.. is a big problem.. if you have that many.. that is why yoru grass is dying ....

if this is the only one you found.. get over it.. lol ... no need to poison mother earth.. until you have a plague ...

you dont mention where you found it.. or what crop is associated with it.. lawn treatments would not be good in a veg patch ....

and no.. i have no faith it bt ....

ken

As already mentioned, where you found it and how many there are are important considerations. Yes, grubs eat plant roots, and some will grow up into beetles that will feast on your plants ... while others grow up into beetles that will feast upon insects that are damaging your plants. If you want to ID the grub, best bet is to take it to your local county office of your State Cooperative Extension Service. Definitive ID of grubs is made by examining the pattern of rasters (coarse hairs) on their rear end.

Thank you all for answering. As a follow up, it was found in my vegetable garden and is pretty heavily infested. I don't have anything growing in there yet, but I was hoping to put in some 4 inch plants to teach my son to appreciate and eat vegetables.

In a prior season, the vegetable garden had tomatoes and sweet peppers growing in it.

Japanese Beetle or June Bug.
Former is introduced pest. Look for a bronze and metallic green beetle about the size of a bee. Eats everything!!
Whenever I find grubs, I put them in the bird feeder. What a feast they have.
Milky Spore will target and kill Japanese Beetle grubs and nothing else. It is easily obtained online and seems to work.
John

Sigh.....didn't you notice where the OP is from, leafhead? And as jean said earlier...."Ignore any comments which say you have Japanese Beetles."

twang,
here are some pictures that might help you to identify the insect and to decide whether it is harmless or not.